1. Field of the Invention
The present invention relates generally to the field of aquatic pollution, and more particularly, but not by way of limitation, to an apparatus for rapidly determining the biochemical oxygen demand of a liquid at an on-site location.
2. Brief Description of the Prior Art
Biochemical oxidation demand (BOD) is widely used in measuring aquatic pollution. For example, the performance of wastewater treatment plants is generally monitored by measuring the efficiency of BOD removal.
One of the major problems encountered in use of the conventional BOD test is that the test generally requires five or more days to run, a time period which is too long for use in process control. Other tests, such as the total organic carbon (TOC) and chemical oxidation demand (COD) measure total organic matter, but such tests do not provide a valid measure of biologically degradable organic matter.
A key feature of the BOD test as a measure of the total biologically degradable organic matter is sequential uptake, commencing with labile and ending with refractory compounds. Studies of biofilms have suggested that the oxidation of complex mixtures of organics in fully oxygenated biofilms proceeds sequentially as substrate diffuses into the biofilm in a manner similar to uptake in plug-flow activated sludge units or in the conventional BOD test. As the result of such studies, biofilm BOD electrodes have been developed for use in rapid measurements of wastewater samples.
While initial studies using the biofilm BOD electrode or probe have exhibited favorable results, the use of such probes to make rapid BOD measurements at on-site locations has been difficult because of the auxiliary equipment required in carrying out the test. Further, the biofilm BOD electrode or probe suffers from the disadvantage that it is not acclimated to the effluent being tested, and is unstable.
Thus, while some advance has been made in the art in developing apparatus for the rapid BOD measurements, the need still remains for an apparatus which can be employed to rapidly measure the BOD of a liquid sample at an on-site location, which is dependable and simple in operation, easily transported, and economical to manufacture. It is to such apparatus that the present invention is directed.